Mention open tunings and some guitarists’ eyes glaze over – especially if they’re from the rock world, where standard tuning lives up to its name or, perhaps, dropped D or even-tempered half- or whole-step across-the-fretboard detuning comes into play.

But in blues and folk music, and in some of Led Zeppelin’s greatest recordings like “Kashmir,” which is in D-A-D-G-A-D, open tunings can create a brave new world of sounds, albeit for an old-world-based technique.

Simply defined, an open tuning is one that allows a chord to be played by strumming a guitar’s unfretted strings. Since a chord is a cluster of notes, that definition leaves a lot of room for interpretation. A tuning like open G, used by the Delta legend Son House for his classic “Death Letter Blues” and by Keith Richards in “Honky Tonk Women,” will have a sound that seems timeless. But check out Sonic Youth’s “Dirty Boots” or Glenn Branca’s Symphony Number 3 to hear how unconventional – but gloriously musical – open tunings can sound.

For comfort’s sake, the coolest open tunings for beginners are open D, open E and open G. So here are a few quick tips for diving headlong into each.

Open DThis tuning has two typical variations, D-A-D-F#-A-D and D-A-D-G-A-D. The former is more closely associated with traditional blues; the latter with folk music from the British Isles and Appalachia. Strike all six strings of your guitar in either one and dig how low the sound goes and how those rumbling tones hang in the air.

It’s a piece of fantastic, fluffy, fudge-frosted chocolate cake to play any basic chord progression in open D, E and G tunings. The I-IV-V progression, for example, can be played with just the index finger using the open position, fifth and seventh frets.

For an example, check out Charley Patton’s 1929 Delta blues classic “Spoonful,” not to be confused with the Cream track, which is based on the later Howlin’ Wolf recording on Chess Records. Listen to the bold dark notes that reel from Patton’s guitar and the thick, cutting tone of his slide.

More on slide in a moment, but let’s take a quick look at D-A-D-G-A-D. The G resonates just a bit higher than F#, of course, but the third string’s different ringing overtones change the entire harmonic vibe of the tuning. Since Gibson Les Paul legend Jimmy Page’s early playing in Led Zeppelin took as much inspiration from British folk music as American blues, his performances on “Kashmir” and “Black Mountain Side” provide sterling examples. The open D-A-D-G-A-D tuning also lends itself to producing the drone tones heard on the latter, giving the song a bonus Eastern feel.

Open EElmore James and his disciple Duane Allman both favored open E, which is E-B-E-G#-B-E. But it’s there in Slash’s Les Paul on Guns N’ Roses’ “It’s So Easy” and The Rolling Stones’ “Jumpin’ Jack Flash,” too. Open D’s brighter sounding cousin, open E is especially serviceable for slide. Whether using a slide made of steel, glass, ceramic, or, really, any suitable material, the tuning makes tones shimmer with full chords, triads or single notes.

Allman’s exuberant slide guitar playing with his cherry red Gibson SG on “Statesboro Blues” from the Allman Brothers Band’s Live At the Fillmore may be the definitive electric slide rock-era performance in open E. But Allman’s exquisitely chiseled sound was the result not only of his choice of tunings, but his distinctive palm-muting, the exact pressure Allman applied to his strings and other highly idiosyncratic factors that are part of an extremely well-developed signature style.

Open GIt’s back to blues bedrock for open G, referred to by many of the historic Delta players as “Spanish” tuning. This one goes D-G-B-G-B-D. The hitch for novices is watching that low D string. Hit it with any of the open chords below the fifth fret and a very unmagical sound happens – unless, of course, you’re looking for some crazy dissonance. That’s why some players who work extensively in open G, most famously Keith Richards, take the low string off their guitars. The Stones’ “Wild Horses” is a great example of open G at its most pastoral, and a sharp contrast to that is the equally acoustic slash-and-burn roughhouse recordings of Son House playing “Death Letter.” On the rock tip, listen to Richards’ rhythm guitar in “Brown Sugar,” where open G provides the song’s distinctive ringing chords.

Playing in open G is a bit more complex than the open D and E family, which the old blues players referred to as “vestopol” style tunings. While the string relationships are more consonant in open D and E, things can get pretty hairy initially while attempting to play single note lines in open G.

In open D, in particular, the fourth and fifth strings are tuned the same as in standard tuning, which gives players more used to standard tuning a springboard for building a new map of scales and licks on the fretboard. Of the three most popular opening tunings explored here, getting good at playing in open G is lot like getting to Carnegie Hall. It takes lots of practice.